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Infectious diseases > LAB EXAM #2 > Flashcards

LAB EXAM #2 Flashcards

1
Q

What does all bacteria require to grow successfully in vitro?

A

Water, carbon, an energy source, nitrogen and minerals including phosphorus, sulphur and trace elements.

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2
Q

Solid medias containing agar?

A

Complex carbohydrate from red algae, less that 2% supports bacterial growth. The agar will liquify @100 degrees and remind liquid until 42 degrees. Once cooled and solidified, can be heated up to 100 degrees before liquifying again.

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3
Q

Why can you only use distilled or deionized what’re to rehydrate culture media?

A

Tap water may be contaminated with chemicals that effect the quality and reproducibility of the medium.

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4
Q

What does it mean for microorganisms to be ubiquitous?

A

Found everywhere in our environment, growth requirements vary considerably.

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5
Q

What are the 5 different types of physical requirements for bacterias oxygen needs/requirements?

A
  1. Strict aerobe - requires atmospheric oxygen to grow.
  2. Strict anaerobes - grow in complete absence of oxygen
  3. Facultative anaerobes - can grow in either but prefers environments with oxygen
  4. Aerotolerant anaerobes - grows with and without the presence of oxygen
  5. Microaerophiles - only gowns when oxygen is available in a low concentration.
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6
Q
  1. How do Candle Jars work?

2. What are they used for?

A
  1. Inoculated plates are placed inside an airtight jar with a candle. The burning of the candle uses up a sufficient amount of oxygen, it will go out leave 5-10% oxygen within the candle jar.
  2. Used for Microaerophiles
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7
Q

What % oxygen is atmospheric?

A

20%

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8
Q

How is an anaerobic jar used?

A

Inoculated Petri dish is added inside along with a hydrogen-generating envelope. H4 + O2 -> H2O, decreasing the O2 in the jar. The oxygen indication (Methylene clue dye) is placed in jar, the oxygen indicator will fade as H2O is created.

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9
Q
  1. What is Sodium thioglycollate?

2. What is it used for?

A
  1. A reducing agent that removes O2 via a chemical rxn
  2. 0.5% agar is added to prevent diffusion of 02 into localized bacterial growth. Methyl blue is added and will turn colourless (no oxygen) to blue/green when oxygen is present.
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10
Q

What does the optimum temperature for a bacteria tell us?

A

Heat sensitivity of its enzyme systems.

Low temp = inactive, high temp = denature (damage or death)

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11
Q

What is dry heat?

A

Ovens = denature enzymes, dehydrates microbes, killed via oxidation effects.

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12
Q

Moist heat?

A

Ex. Pasteurization, boiling, autoclave

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13
Q

What is autoclave tape?

A

Heat sensitive dye strips when preferred temperature is reached, the dye will become visible.

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14
Q

What is a spore strip?

A

Filter paper impregnated with heat resistant spores of Geobacillus stearothermophilus placed in the centre of autoclave, then placed in broth medium , incubated.

If autoclave functions properly, there will be no growth.

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15
Q

What is ionizing radiation?

A

Electromagnetic radiation can have short wavelengths = high energy which can cause an atom to loose electrons. Lower levels can cause mutations.

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16
Q

What are gamma rays?

A

(<1.0nm) used for sterilization due to the ability of killing spoilage organisms, inactivating enzymes involved in spoilage.

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17
Q

What is ultra-violet radiation?

A

(10-400nm) 260nm is the most harmful to microorganisms due to it being absorbed into its DNA.

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18
Q

How does ultra-violet light effect DNA within the microorganisms?

A
  • forming thymine dimers (Two thymin strands covalently bonded) which effects DNA replication and transcription during protein synthesis.
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19
Q

What are the 4 main types of diagnostic tools when trying to identify an organism responsible for an infection?

A
  1. Staining and microscopy (Gm stain, Lab #2)
  2. Growing in Culture = biomedical testing (Lab #34578)
  3. DNA/RNA detection using PCR and RT-PCR
  4. Immunological methods (detect antigens or antibodies)
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20
Q

What is indigenous or normal flora?

A

Population of microorganisms that live in/on the human body, usually w/out causing disease.

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21
Q

What are communal microbiota?

What are opportunistic pathogens? Å

A

CM: feed on exreted cellular waste and dead cells w/out causing harm.

OP: normally symbiotic but if immune diffidency occurs they can become harmful.

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22
Q

What are nosocomial infections?

A

Ones that occur in health care settings

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23
Q

Streptococcus progenies (Lancefield Group A (GAS))

A
  • cultured from the throat
  • responsible for pharyngitis (Strep throat), variety of skin infections and sequelae (Scarlett fever, TSS)
  • produces the enzyme hemolysin - degrade RBC, Bloop agar plates will turn clear = beta hemolysis
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24
Q

What is stereotyping?

A

The method of identifying a pathogen based off their specific antigens.

This is done by mixing a suspension of organism or antigen extracted from the organism with the antibodies. (Reaction between antibodies and antigen will occur) The rxn will cause a 3 dimensional aggregation which will become macroscopic (Visible to the eye)

25
Q

How does the humonal immune system react?

A

Produce antibodies

26
Q

Antigens vs antibodies?

A

Antigens: Foreign cellular components that stimulate antibody production

Antibodies: proteins the specifically react with foreign materials.

27
Q

What is the purpose of the ELISA test?

A

To visually show reaction between antigen and antibody. Can also test for hormones.

28
Q

What are the 4 steps to to ELISA?

A
  1. Plastic wells are coated with the Purified HIV antigen which will bind to the wells creating an immunosorbent assay (proteins targa absorbed to wells)
  2. Patient sera is added, if antibodies are present, they will bind to the antigens and will remain even after washing.
  3. A solution containing non-specific anti-IgG (secondary antibody) is added to bind the patient’s HIV antibody (primary).
  4. After washing solution on taking chromogenic (colour producing) enzyme substrate is added. If bonded (HIV antibodies present - BLUE)
29
Q

What is Epidemiology?

A

The study of occurrence, spread and control of disease.

30
Q

What are the 3 determinants of an infectious diseases POV: epidemiological worker?

A
  1. Dose - # of microbes entering the body
  2. Virulence - ability of the microbe to cause disease
  3. Resistance - the ability for the body to defend itself against a specific microbe.
31
Q

What does the organism Colifom indicate?

A

It’s presence indicates the presence of fecal material.

32
Q

Coliform?

A
  • Gm-
  • Non-sporting rods
  • faculatative (occurring optionally in response to circumstances rather than by nature.)
  • Able to ferment lactose to acid and gas in 48hr, @35 degrees
33
Q

Food infections vs intoxications?

A

Infections: ingestion of microbes

Intoxications: ingestion of microbial toxins

34
Q

What are 5 ways of avoiding food - borne illness at home?

A
  1. Shopping: check expiration dates, avoid cross- contamination, was bags and refrigerate/freeze food immediately.
  2. Storing: fridge @ 4 degrees, freezer @ -18 degrees. Refrigerate left overs, date food. Freeze meat if not using in 2-3 days
  3. Preparing food: wash hands, surfaces, utensils, thaw food in fridge, wash produce, avoid cross contamination.
  4. Cooking: cook meat and eggs fully and serve immediately.
  5. Cleaning: Wash everything
35
Q

What is Diagnostic or clinical microbiology?

A

The ability to diagnose infectious disease through microscopic examination, culture and identification, serological testing and molecular testing (newer)

36
Q

How does the culture and sensitivity test work?

A

A specimen is cultures on a media appropriate for pathogens, then antibiotic sensitivity will be determined after the addition of antibiotic discs are aseptically added and after 48hr.

37
Q

What are the 4 important factors to remember during collection and transport?

A
  1. Must not be contaminated
  2. Timing due to antibiotics medication
  3. Proper labelling
  4. Brought to bad immediately.
38
Q

Where will most specimens be cultured/placed on? (Lab 8a)

A
  • All-purpose, nonselective enriched mediums (ex. BAP)

- selective and/or differential media (for closely related microorganisms)

39
Q

What is the optimum temp + atmosphere for human-associated bacteria?

A

37 degrees, 5% CO2 - can be created in a candle jar or anaerobic jar or chamber

40
Q

What is the identification of bacteria based on?

A

Cellular morphology (Shape, size, cellular arrangement, GM stain, capsules/spores), colony morphology (Colony shape, size, colour, margin, and texture on specific media), and physiology (biochemical characteristics and serological typing.

  • Metabolic characteristics must also be studied.
41
Q

The ability of an organism to use particular cmpd as a nutrient source anfd form it into waste I’d determined by what?

A

Genetic information that the organism carries, can be used for taxonomic identification.

42
Q

What is taxonomic identification?

A
  • Observation of oxygen requirements, substrate utilization, growth factor requirements, end products formed, ability to grow under certain conditions of pH and temperatures.
  • Able to identify genus and species
43
Q

What are the 3 different ways to perform biochemical tests?

A
  1. Individual test tubes
  2. Miniature test blanks (API 20E)
  3. Automated systems (Vivek systems)
44
Q

What is a citrate test?

A

Inoculating bacteria into synthetic medium in which sodium citrates is the ONLY source of carbon
+ energy. If the bacteria can produce the enzyme citrase, it will be able to grow on the plate. Plate contains pH indicator bromethyl blue and will turn from green to blue when enzyme presence due to the basic shift in pH from byproducts of citrase.

45
Q

What common bacteria is able to produce the citrase enzyme?

A

Environmental coliforms

NOT FECAL COLIFORMS

46
Q

How does the Indole test work?

A

Determines whether or not a bacterial species is able to degrade the amino acids tryptophan to use as carbon, nitrogen and an energy source. The enzyme tryfprophanase breaks down tryptophan to produce pyruvate, ammonia and indole. Indole is detected by Kovacs reagent (added in plate) will turn bright pink.

47
Q

How does urease detection work?

A

Microorganisms that are able to produce the enzyme urease splits into ammonium and CO2, the pH indicator phenol red will turn from pale orange to bright pink when urea is hydrolyzing (accumulation of NH+)

48
Q

How does the Gelatine test work?

A

Gelatos is a fibrous protein, microorganisms that produce the enzyme gelatinase is able to break down the gelatin into amino acids and nutrients, hydrolyzing it into a liquid

49
Q

How does the API 20E system work?

A

Provides a standardized battery of different media and used to identify GM- bacilli from the enterobacteriaceae family.

50
Q

What is the API 20E system made up of?

A

20 micro tubes containing dehydrated biochemical substrates. When bacteria is added suspended in sterile saline. An anaerobic environment is created after adding the sterile mineral oil. After 18-24hr + incubation in a humidified trey, results are read via colour change (+/-) with analytical profile index book to identify microorganisms.

51
Q

What is the purpose of performing an antibiotic sensitivity using the Kirby Bauer system?

A

To test the organism against antibiotics to see if they could be used to treat infection at the specimen site for suspected pathogen.

52
Q

What are the 3 categories for optimal temperatures for growth parameters?

A

Psychrophiles - 5-20 degrees
Mesophiles - 20-45 degrees (human)
Thermophiles - 25-95 degrees

53
Q

When exposed to UV light, why was B. Sub able to have isolated colonies?

A

B.sub was able to create spores when stressed out BEFORE UV.

54
Q

How many coliform are acceptable in drinking water?

A

<1/l00mL

55
Q

How many coliform are acceptable in water that people swim in?

A

< 200/100mL

56
Q

What are the ingredients in a m-Endo plate?

Is it a selective or differential plate?

A
  1. Peptone, dipotassium hydrogen phosphate, LACTOSE, anhydrous sodium sulfite, agar
  2. Both. Selective and differential due to
    - inhibits GM+
    - pH indicator that will turn dark red/green when bacteria can produce lactase.
57
Q

What are minimum 3 factors other than Kirby-Bauer results that should be considered when determining which antibiotic to use?

A
  • toxicity/side effects
  • allergies
  • spectrum of activity
  • Method of dosing (Oral or IV)
58
Q

Tube biochemical test vs API 20E test, pros and cons?

A

TUBE: less room for error, see if organism is able to produce certain enzymes, less chance of contamination.

API 20E: rapid identification of specific bacteria, cheep, easier (20 tests to 20 tests), uses only one colony

Infectious diseases (3 decks)

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